1. Technical Field
The present invention relates to an image forming apparatus such as a copying machine, a printer, a FAX and a composite machine having two or more of their functions, and more particularly, to an image forming apparatus using a stepping motor (often called a step motor or a pulse motor) as the motor for driving a rotor.
2. Related art
The related image forming apparatus has a rotor that is driven and rotated such as a sheet conveying device, a photosensitive body, a developing unit, a transferring unit, a fixing unit, or an intermediate transfer belt, and a DC motor or a stepping motor is employed as the motor for driving the rotor. The stepping motor is the motor for driving the rotation in accordance with the input of pulses, and suitably employed for controlling precisely the rotation of the rotor.
However, the stepping motor has a problem that a so-called step-out phenomenon occurs in which the rotation of the motor does not follow an input pulse train when the rotation load of the rotor is large.